Commit 7ae731a8 authored Jun 09, 2020 by Dan Carpenter Committed by Greg Kroah-Hartman Jul 10, 2020

lib: devres: add a comment about the devm_of_iomap() function

We recently introduced a bug when we tried to convert of_iomap() to
devm_of_iomap(). The problem was that there were two drivers mapping
the same io region. The first driver was using of_iomap() and the
second driver was using devm_of_iomap() and the kernel booted fine.
When we converted the first drive to use devm_of_iomap() then the second
driver failed with -EBUSY and the kernel couldn't boot.

Let's add a comment to prevent this sort of mistake in the future.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20200609104642.GA43074@mwanda

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 35bd8c07

lib/devres.c

+6 −0

Original line number	Diff line number	Diff line
		@@ -213,6 +213,12 @@ void __iomem devm_ioremap_resource_wc(struct device dev,
		* base = devm_of_iomap(&pdev->dev, node, 0, NULL);
		* if (IS_ERR(base))
		* return PTR_ERR(base);
		*
		* Please Note: This is not a one-to-one replacement for of_iomap() because the
		* of_iomap() function does not track whether the region is already mapped. If
		* two drivers try to map the same memory, the of_iomap() function will succeed
		* but the the devm_of_iomap() function will return -EBUSY.
		*
		*/
		void __iomem devm_of_iomap(struct device dev, struct device_node *node, int index,
		resource_size_t *size)

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